1. Field of the Invention
This invention relates to direct-current (DC) brushless motors, and more particularly, to a stator structure for use in miniaturized DC brushless motors.
2. Description of Related Art
In this information age, office automation devices such as personal computers (PC) and other accessaries are becoming indispensable tool both at offices and home. For heat dissipation need, all these devices require the use of miniaturized brushless motors. For volume reduction need, the miniaturization of brushless motors become more and more important.
FIG. 1 shows an exploded perspective view of a conventional stator structure and the associated rotor structure for a DC brushless motor, which is disclosed in U.S. Pat. No. 5,093,599. In that patent, for the miniaturized fan motor, the stator-poles construction thereof is made of one sheet. As shown in FIG. 1, the stator structure includes a self-lubricating bearing 1, a sleeve tube 2, a ring coil 3, an upper stator-pole piece 4a, and a bottom stator-pole piece 4b, components 2, 4a, and 4b are made of permeable materials for miniature motor, 4a and 4b are not laminated that is say 4a, 4b are single sheeted, while the associated rotor structure includes a shaft 5, a rotor magnet 6, and a circuit board 7.
The sleeve tube 2 is a tubular member having a large-diameter portion in the center and two small-diameter portions on the two ends thereof. The small-diameter portions are used to axially mount the upper and bottom stator-pole pieces 4a, 4b thereon.
As illustrated in FIG. 3A, when the upper and bottom stator-pole pieces 4a, 4b are axially mounted the sleeve tube 2, there are two interfaces, as respectively indicated by the reference numerals 10a and 10b, formed therebetween. The drawback in the prior art stator structure is its complex structure. For example the sleeve tube 2 is formed by lathing, which causes the manufacturing work laborious to carry out. Moreover, since the stator structure is composed of a large number of components, the manufacturing cost of the brushless motor is high. Briefly, this invention can simplied the motor structure with minimized motor size without reducing the motor performance